Have you noticed that while you're on a phone call on Xiaomi Redmi 9, the screen stays on, even though it used to go out automatically? Not only is this an annoying problem, it also drains the battery quickly, and accidental cheekstrokes can interrupt the call or activate unwanted functions. Most of the time, the proximity sensor is to blame, but there are other reasons, from incorrect settings to hardware malfunctions.
In this article, we'll look at all the possible reasons why the Redmi 9 screen doesn't dim when you talk, and give you step-by-step instructions to fix them, how to check the proximity sensor, reset your phone without losing data, and what to do if the problem is physical damage to your smartphone, and at the end, answers to frequent questions and prevention tips.
1.How the proximity sensor works and why it might break
The proximity sensor in Xiaomi Redmi 9 is responsible for automatically turning off the screen when you hold the phone to your ear. It works on the basis of infrared radiation: when an object (like your head) approaches the top of the smartphone, the sensor detects this and sends a signal to the system to extinguish the display.
If the sensor fails or is not working properly, the screen stays on during the call, and the reasons can be different:
- 🔹 Sensor pollution – dust, sweat, or protective film blocks infrared signal.
- 🔹 Software failure – firmware errors or application conflict interfere with the correct operation of the sensor.
- 🔹 Physical damage – a phone drop or moisture hit could have knocked the sensor out.
- 🔹 Incorrect settings – accidentally disabling a feature in the phone menu.
Before you sin on a hardware breakdown, it is worth checking whether the sensor is turned off in the settings, sometimes the problem is solved in just two clicks.
2. Testing of the proximity sensor: step-by-step instruction
To make sure that the proximity sensor is working correctly, use Xiaomi’s hidden test menu.
- Open the Phone app.
- Enter the combination: ##6484### (or #4636## for older versions of MIUI).
- Select the Hardware Testing option → Proximity Sensor.
- Close the top of the phone with your hand – if the sensor is working, the screen should go out, and with the hand removed – light up again.
If the screen doesn't respond to the hand, the problem is the sensor, and if the test is successful, but the screen still doesn't go out during the call, look for the reason in the settings or software failures.
Close the sensor with your hand in the test menu|Check the cleanliness of the top panel of the phone|Make sure there is no protective film above the sensor.|Reboot your phone after the test-->
You can also use third-party apps to check, like the Sensor Test or the Phone Doctor Plus from Google Play, to see if the system recognizes an object approaching.
3. phone settings that may interfere with the sensor
Sometimes the problem isn't with the sensor itself, but with the MIUI settings that are wrong.
- Go to Settings → System and Device → Additional Settings → Special Features → Physical buttons.
- Make sure the option to turn off the screen when approaching (or Proximity sensor) is enabled.
- Check Settings → Screen → Sleep and Lock – there should be no restrictions on automatically turning off the display.
If you use third-party launchers (like Nova Launcher or POCO Launcher), they can also conflict with the sensor. Try temporarily returning a standard MIUI launcher and check if the problem persists.
| Setting up | Wherever | Recommended value |
|---|---|---|
| Turn off the screen when approaching | Settings → Special. capabilities → Physical buttons | Included. |
| Automatic locking | Settings → Screen → Sleep and lock | 30 seconds or less |
| Do not disturb mode. | Settings → Sound and vibration → Do not disturb | Off or set to exceptions |
| Energy conservation | Settings → Battery → Energy saving mode | Disabled for the test |
If after checking all the settings the problem remains, proceed to the next step - reset the cache or update the firmware.
4. Software glitches: cache, updates and reset settings
The proximity sensor may be affected by a contaminated cache or outdated firmware.
- 📲 Cache Clearing: Go to Settings → Annexes → Application management. Find the phone and press Clear cache. Repeat Settings for the app.
MIUI Update
Go to Settings → About Phone → Update the system and install the latest patches. Often newer versions fix sensor bugs.
Resetting settings
Go to Settings → System & Device → Additional Settings → Reset and select Reset All Settings. This will return your phone’s settings to factory settings, but will not affect your files.
If the sensor went off after this manipulation, it was the software that was the problem, and if it wasn't, it might need a more in-depth diagnosis.
What if the problem returned after resetting?
Physical causes: pollution, moisture, damage
If the software doesn't work, you should look at the phone for physical damage, and the proximity sensor is at the top of the screen, next to the speaker, and it's often disrupted by:
- 🧴 A protective film or glass covering the sensor, try to carefully remove the film in the sensor area (usually a small circular hole next to the front camera).
- 💦 If the phone fell into water or was in high humidity, the sensor could oxidize.
- 💥 Hit or fall. Even if the screen is intact, the internal components could have shifted.
To check if something is disturbing the sensor, take a flashlight and shine it on the top of the phone. If you see a cloudy spot or contamination in the sensor area, clean it gently with a soft wipe (do not use alcohol or abrasive materials!).
⚠️ Warning: If you suspect that the sensor is physically damaged (for example, after a fall), do not try to disassemble the phone yourself. In the Xiaomi Redmi 9, the proximity sensor is often integrated into the display module, and its replacement requires special equipment.
6. Alternative solutions if the sensor is not working
If all attempts to bring the sensor back to life were unsuccessful, you can use workarounds:
- 🔘 Manual screen shutdown: Press the power button during the call to lock the screen. uncomfortable but works.
- 📱 Crutch apps: Google Play has utilities like Proximity Sensor Fix or Gravity Screen that emulate the sensor. They're not perfect, but they can temporarily fix the problem.
- 🔧 Replacement of the display module: If the sensor fails permanently, it will cost 1,500-3,000 rubles (depending on the service). For Redmi 9, this is one of the most frequent breakdowns after falls.